Invited Article: Generation of one-million-mode continuous-variable cluster state by unlimited time-domain multiplexing

Yoshikawa, Jun–ichi; Yokoyama, Shohei; Kaji, Toshiyuki; Sornphiphatphong, Chanond; Shiozawa, Yu; Makino, Kenzo; Furusawa, Akira

doi:10.1063/1.4962732

Cited by 248 publications

(240 citation statements)

References 35 publications

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“…The control of large entangled states has been achieved experimentally [18,19]. Small-scale algorithms have been demonstrated, including alternative computational models based on quantum walks.…”

Section: Status and Challengesmentioning

confidence: 99%

The quantum technologies roadmap: a European community view

et al. 2018

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Within the last two decades, quantum technologies (QT) have made tremendous progress, moving from Nobel Prize award-winning experiments on quantum physics (1997: Chu, Cohen-Tanoudji, Phillips; 2001: Cornell, Ketterle, Wieman; 2005: Hall, Hänsch-, Glauber; 2012: Haroche, Wineland) into a cross-disciplinary field of applied research. Technologies are being developed now that explicitly address individual quantum states and make use of the 'strange' quantum properties, such as superposition and entanglement. The field comprises four domains: quantum communication, where individual or entangled photons are used to transmit data in a provably secure way; quantum simulation, where well-controlled quantum systems are used to reproduce the behaviour of other, less accessible quantum systems; quantum computation, which employs quantum effects to dramatically speed up certain calculations, such as number factoring; and quantum sensing and metrology, where the high sensitivity of coherent quantum systems to external perturbations is exploited to enhance the performance of measurements of physical quantities. In Europe, the QT community has profited from several EC funded coordination projects, which, among other things, have coordinated the creation of a 150-page QT Roadmap (http://qurope.eu/h2020/qtflagship/roadmap2016). This article presents an updated summary of this roadmap.

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Section: Status and Challengesmentioning

confidence: 99%

The quantum technologies roadmap: a European community view

et al. 2018

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“…Although small-scale quantum circuits with various qubits have been demonstrated [3,4], a large-scale quantum circuit that requires scalable entangled states is still a significant experimental challenge for most candidates of qubits. In continuous variable (CV) QC, squeezed vacuum (SV) states with the optical setting have shown great potential to generate scalable entangled states because the entanglement is generated by only beam splitter (BS) coupling between two SV states [5]. However, scalable computation with SV states has been shown to be difficult to achieve because of the accumulation of errors during the QC process, even though the states are created with perfect experimental apparatus [6].…”

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confidence: 99%

Analog Quantum Error Correction with Encoding a Qubit into an Oscillator

2017

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To implement fault-tolerant quantum computation with continuous variables, Gottesman-Kitaev-Preskill (GKP) qubits have been recognized as an important technological element. However, the analog outcome of GKP qubits, which includes beneficial information to improve the error tolerance, has been wasted, because the GKP qubits have been treated as only discrete variables. In this Letter, we propose a hybrid quantum error correction approach that combines digital information with the analog information of the GKP qubits using a maximum-likelihood method. As an example, we demonstrate that the three-qubit bitflip code can correct double errors, whereas the conventional method based on majority voting on the binary measurement outcome can correct only a single error. As another example, we show that a concatenated code known as Knill's C 4 =C 6 code can achieve the hashing bound for the quantum capacity of the Gaussian quantum channel (GQC). To the best of our knowledge, this approach is the first attempt to draw both digital and analog information to improve quantum error correction performance and achieve the hashing bound for the quantum capacity of the GQC. DOI: 10.1103/PhysRevLett.119.180507 Quantum computation (QC) has a great deal of potential [1,2]. Although small-scale quantum circuits with various qubits have been demonstrated [3,4], a large-scale quantum circuit that requires scalable entangled states is still a significant experimental challenge for most candidates of qubits. In continuous variable (CV) QC, squeezed vacuum (SV) states with the optical setting have shown great potential to generate scalable entangled states because the entanglement is generated by only beam splitter (BS) coupling between two SV states [5]. However, scalable computation with SV states has been shown to be difficult to achieve because of the accumulation of errors during the QC process, even though the states are created with perfect experimental apparatus [6]. Therefore, fault-tolerant (FT) protection from noise is required that uses the quantum error correcting code. Because noise accumulation originates from the "continuous" nature of the CVQC, it can be circumvented by encoding CVs into digitized variables using an appropriate code, such as Gottesman-KitaevPreskill (GKP) code [7], which are referred to as GKP qubits in this Letter. Menicucci showed that CV-FTQC is possible within the framework of measurement-based QC using SV states with GKP qubits [6]. Moreover, GKP qubits keep the advantage of SV states on optical implementation that they can be entangled by only BS coupling. Hence, GKP qubits offer a promising element for the implementation of CV-FTQC.To be practical, the squeezing level required for FTQC should be experimentally achievable. Unfortunately, Menicucci's scheme still requires a 14.8 dB squeezing level to achieve the FT threshold 2 × 10 −2 [8][9][10]. Thus, another twist is necessary to reduce the required squeezing level. It is analog information contained in the GKP qubit that has been overlooked. Th...

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“…For (3)- (5) we envision leveraging several mechanisms: Human representation (3) encoded as keys over a large number of entangled states (Yoshikawa et al 2016) with (4) nonlocal multiplayer games (eg CHSH (Winter 2010)) and (5) zero-knowledge proof protocols within a HoTT formulation of closed-loop cybernetic control systems (Baez and Erbele 2015) (Aaronson 2016). We look forward to fleshing out further details with interested parties at the AICS workshop.…”

Section: Embedding 'Immortality' Into Finite Systemsmentioning

confidence: 99%

Engineering permanence in finite systems

Bilar

2016

Preprint

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The man-machine integration era (MMIE) is marked by sensor ubiquity, whose readings map human beings to finite numbers. These numbers processed by continuously changing, optimizing/learning, finite precision, closed loop, distributed systems are used to drive decisions such as insurance rates, prison sentencing, health care allocations and probation guidelines. Optimization and system parameter tuning is increasingly left to machine learning and applied AI. One challenge we face is thus: Ensuring the indelibility, the permanence, the infinite value of human beings as optimization-resistant invariants in such system environments. In this challenge paper, we propose developing safeguards, specifically working towards a 'deontological imprimatur' architecture embedding resilient AbstractThe man-machine integration era (MMIE) is marked by sensor ubiquity, whose readings map human beings to finite numbers. These numbers-processed by continuously changing, optimizing/learning, finite precision, closed loop, distributed systems-are used to drive decisions such as insurance rates, prison sentencing, health care allocations and probation guidelines. Optimization and system parameter tuning is increasingly left to machine learning and applied AI. One challenge we face is thus: Ensuring the indelibility, the permanence, the infinite value of human beings as optimizationresistant invariants in such system environments. In this challenge paper, we propose developing safeguards, specifically working towards a 'deontological imprimatur' architecture embedding resilient representations of human beings.

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Invited Article: Generation of one-million-mode continuous-variable cluster state by unlimited time-domain multiplexing

Cited by 248 publications

References 35 publications

The quantum technologies roadmap: a European community view

The quantum technologies roadmap: a European community view

Analog Quantum Error Correction with Encoding a Qubit into an Oscillator

Engineering permanence in finite systems

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